Annealing furnace



Sept 29, 1931. H. ALINDEF! ET AL 1 ,825,380

ANNEALING FURNACE Filed July 23, 1928- '7' Sheets-Sheet l WITN 5555 S game WW ,mmu

Sept. 1931. H. ALINDER ET AL 1,825,380

ANNEALING FURNACE Fil ly 23. 1928 v Sheets-Sheet 2 Mm ESSES INVENTORQ: m

Sept. 29, 1931.

WITNESSES H. ALINDER ET AL ANNEALI'NG' FURNACE Filed July 25, 1928 7 Sheets-Sheet 5 INVENTORS:

Sept. 29, 1931.

WITNESSES H. ALINDER ET AL ANNEALING FURNACE Filed July 25, 1928 7 Sheets-Sheet 4 INVENTORJJ V Sept. 29, 1931.

H. ALINDER ET AL 1,825,380

ANNEALING FURNACE Filed July 23. 1928 7 Sheets-Sheet 5 J Z my. 5 1f: I r ./,2I P'"? if 91 WITNESSES v INVENTORS',

Sept. 29, 1931.

H. ALINDER ET AL 1,825,330

ANNEALING FURNACE Filed July 25, 1928 7 Sheets-Sheet 6 WITNESSES Sept. 29, 1931. AUNDER 1,825,380

ANNEALING FURNACE Fil ed July 23. 1928 7 Sheets-Sheet 7 WITNESSES atented Set. 2%, 1931 HENRY ALTNDER AND GRANT B. SHIPLEY, 01E PITTSBURGH, PENNSYLVANTA, AS-

SIGNORS, BY MESNE ASSIGNMENTS, TO THE INTERNATIONAL NICKEL COMPANY, TING, 0F NEW YORK, N. Y., A CORPORATION OF DELAWARE ANNEA'LING FURNACE Application filed. July 23, 1928, Serial No. 294,777,, and in Great Eritain June 29, 1923.

The invention relates to the continuous annealing of metal in a non-oxidizing or reducing atmosphere. While in its broader aspects it is unlimited to the annealing of any particular metal, or form of it, it is espe* cially applicable to the annealing of sheet metal, and is herein so illustrated and described.

An object of the invention is to provide a continuous annealing apparatus whereby metal may be quickly and eflectively annealed in a non-oxidizing or reducing atmosphere with a minimum loss of the gas or gases forming such atmosphere, and a further object is to make provision for reducing the oxide coating on hot Worked metal while it is being annealed.

The invention is illustrated in the accompanying drawings, of which Fig. 1 is a central longitudinal section of a double deck annealing furnace embodying our invention; Figs. 2, 3 and 4 cross sectional views taken, respectively, along the lines TI][I, TIT TH and TVTV, Fig. 1; Fig. 5 a top plan view of the charging chamber; Fig. 6 an enlarged sectional view of the charging chamber taken vertically along the lineVI-VT, Fig. 5; Figs. 7 and 8 side elevations of the car engaging devices placed between the car tracks at the entrance and exits respectively of the elevators; Fig. 9 a face view of a side wall of the heating zone of the furnace; and Fig. 10 a detail sectional view taken on the line XX, Fig. 9. y

We will first describe the structural features of the furnace shown herein, and then explain its operation and certain features of our invention incident to its operation.

Having reference to the drawings, there is shown in Fig. 1 a double deck continuous annealing furnace consisting of a heating tunnel. mounted upon a supporting structure, there being aloading and unloading track below the tunnel. The furnace proper coinprises a charging chamber 1, an annealing and cooling tunnel 2, and a discharging chamber 3, the tunnel being divided successively into a preheating zone 4, a heating zone 5. a precooling zone 6 and a cooling zone 7 by partial partitions 41. The side walls and top of the charging chainberare constructed of heat insulating material such as fire brick or the like, asare the side walls, tops and bottoms of the pre-heating and heating zones. The bottom portion of the side walls in the heating section of the tunnel are adapted to conform in shape and enclose the truck portion of cars 21. Asbestos strips 102 and 103 (Fig. 2) which are adapted to bear upon the upper portion and the side of the car truck, respectively, are mounted in the sides of the tunnel for preventing the hot gases in the tunnel from passing down between the side of the tunnel and the car body and overheating the car trucks.

The side walls of cooling zone 7 of the tunnel are constructed of heat conducting materials, such as metal plates, so that the heat from the material being annealed will be rapidly carried off. To' expedite such conduction of heat, water jackets 94: are placed around the walls of the cooling zone, and water being circulated about such walls through inlets and outlets 105 and 106 (Fig. 3) in each of the water jackets.

In order that the tunnel may be filled with a non-oxidizing or reducing gas, which is usually lighter than air, and so that material can be inserted into the tunnel and also withdrawn therefrom without causing a substantial loss of such gas, the top, bottom, sides and ends of the furnace are closed eizcept for openings provided. in the bottoms of the end or charging and discharging chambers 1 and 3. In these openings there are elevators 8 and 9, respectively, having floors 10 which form vertically movable bottoms for these chambers. To prevent the gas enclosed in the tunnel from escaping when the elevators are in their upper positions, a depending flange 11 (Fig. 4) is mounted around the edge of the opening in the bottom of each of the end chambers, and a channel or trough-like member 12 adapted to be filled with sand or other sealing material is attached to the edge of the elevator floors and so positioned that flange 11 will embed itself in the sealing material when the elevators are in their raised positions.

The tops of the elevators are provided with false bottoms 13 (Fig. 4) mounted upon supports 14 attached to the elevator carriage, which bottoms close the openings in the bottoms of the end chambers 1 and 3 when the elevators are in their lower positions. A flange 15 is provided around the outer edge of each of the bottoms 13, and a channel 16 containing a sealing medium, such as'sand, is attached to the wall surrounding the opening in the bottom of each end chamber for the reception of flange 15 when the elevator is lowered, thus forming a seal around the false bottom of the elevator when the elevators are in their lower positions.

lliaterial being annealed may be passed through the tunnel in various ways, but in the furnace illustrated cars 21 (Figs. 2,

. 3 and 6) are employed for this purpose. A

track 22 is laid in the bottom of the furnace tunnel 2, and directly below the tunnel within its supporting structure another track 23 is laid (Figs. 1, 2 and On the lower track the material to be annealed is loaded upon, and the annealed material taken from the furnace is unloaded from the cars. The opposite end of the two tracks 22 and 28 terminate in the elevator shafts in which the elevators 8 and 9 are disposed. Both of the car tracks 22 and 23 are customarily filled with cars, and an extra car is provided so that there will be a car in one or the other of the elevators to carry out a cycle of operation presently to be explained.

A pusher rod 31 (Fig. 1) is provided for moving the train of cars through the tunnel, as well as for moving cars into and out of the tunnel. Pusher rods of the type illustrated are so well known in the art that (3?;-

planation of their operating mechanism is deemed unnecessary. An opening 32 (Fig. 6) is provided in the end wall of the charging chamber for reception of rod 31, and, to prevent the enclosed gas from escaping through the opening, a packing 33 is provided. A. pusher rod 35 (Fig. 1), similar to rod 31, is provided for moving the train on the lower track, and is mounted on a level therewith at the end of the discharging elevator shaft.

lhe furnace illustrated is especially adapted for annealing sheet metal or plates. Each car 21 is provided with racks 27 against which the plates to be treated may be placed in an upright position so that the gases in the furnace can freely circulate about them, with the result that their heating and cooling takes place uniformly and at such rate as to make it possible to completely anneal plates while moving the cars step-by-step quite rapidly through the furnace.

At one end of each of the cars there is fixed an end .plate 28, Figs. 2 and 6, which rseaaeo is preferably constructed of heat resisting material and adapted to conform in shape to the openings in the transverse partitions a1 (Fig. 2) formed in the furnace tunnel between its several zones, which are preferably multiples of the length of the cars so that when the cars are at rest end plates 28 of certain cars will substantially close the openings between the zones.

The movements of elevators 8 and 9 may be effected in different ways, but in the furnace illustrated an electric motor 51 (Figs. 5 and 6) is provided and mounted upon the supporting structure on the top of each of the elevator shafts. Motor 51 is connected through a reduction unit 52 to a drive shaft 53, provided at each end with a sprocket wheel 54. Another shaft 55 provided with sprockets 56 ismounted parallel with the shaft 53 but at the end of the furnace, and chains 57 are passed over the sprocket wheels 54 and 56, on each side of the elevators. The outer end of each chain is connected to a counterweight 58, and the other end is connected to the elevator cage, as illustrated. A magnetic brake 61 is mounted between motor 51 and gear reduction unit 52 to engage said shaft for locking the elevator in any desired position. Attached to each side of the elevator cage is a guide frame 62 which is equipped at its upper and lower ends with rollers 63, 64: and 65 which bear upon the plates (56, 67 and G8, respectively, mounted upon guide channels 71 in the elevator shaft.

To avoid interference between the traclrs and the elevator sealing means previously explained, track 25 of each elevator is mounted for longitudinal movements upon the elevator floor, and the ends of tunnel track 22 are set back from the elevator shafts sufficiently to clear sealing means 13 at the top of the elevator cage. Also, provision is made for automatically moving tracks 25 ,so that when an elevator is in its upper and lower positions the track will be brought into registration with track 22 and 23, respectively. For this purpose, the bottom of each rail of track 25 on each elevator is provided with a rack 72 (Figs. 4 and 6) which meshes with a segmental pinion 73 attached to the upper end of an arm 7 4, the lower end of which is attached to a rock shaft 75. To the center of shaft 75 there is attached the upper end of an arm 100 the lower end of which has floating en agement with a longitudinal slidable rod 6 provided with buffer springs 77 and 79. One end of shaft 76 is engaged by the upper end of an arm 78 attached at its lower end to a rock shaft 70 to which there is connected an arm 80 provided with a roller 81 which rides in a cam slot 82 formed in a supporting column 83. Slot 82 is so formed that at the beginning of a downward movement of an elevator it will llf.

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ineeagaeo move the lower end of arm 80 to the right, as viewed'in Fig. 6, which results in track 25 being moved to the right through the train of actuating connections just explained. Track 25 will remain in this position until the elevator approaches its lowermost position where slot 82 is formed to move the track the opposite direction to bring it into registration with track 23 on the lower deck. In this way the end of track 25 clears sealing trough 16, and the end of track 22 is clear of the sealing member 15 at the upper end of the elevator cage.

To prevent a car in the tunnel from moving backwards into the charging chamber,

or one of the cars on the lower traclr from moving backwards into the discharging chamber elevator shaft, car-engaging members 91 (Fig. 7) are mounted between tracks 22 in the tunnel just forward of the charging chamber and in the lower tracks just outside of the discharging chamber elevator shaft. Each of these members consists of a lever 91 provided with a weight at one end and pivotally mounted in a support 92,

the arrangement being-such that a car axle may pass the lever when a car is being moved forwardly, but will be engaged by the lever to prevent the car from moving backwardly.

Between car tracks 22 just inside the tunnel of the discharging chamber, and between tracks 23 just forward of the discharging chamber elevator shaft, there is a magnetically actuated car engaging member 86 (Fig. 8) and a solenoid actuated lever 87 pivotally connected to it. Member 86 is adapted to engage the axles of the cars to prevent their forward movement except when the lever 87 is actuated by the solenoid 88. A circuit, not shown, may be provided to energize each of the solenoids simultaneously with the movements of pusher rods 31 and 35 so that the lever will be released when the trains are moved.

lln the following explanation of the operation of the furnace further features of its construction will be explained. The cars 21 on the forward portion of track 23 are loaded with materials to be annealed, and elevators 8 and 9 are moved to their lower positions. Pusher rod 35 (Fig. 1) is then actuated to move the extra car from discharging chamber elevator 9 and to move forwardly the whole train of cars on the lower track, moving the car at the forward end of the train into charging elevator 8. The elevators are then raised and pusher rod 31 actuated to move the loaded car from charging elevator 8 into the tunnel, and the car from the rear or cooling end of the tunnel into discharging chamber 3 and onto its elevator 9. The elevators are then lowered and the operation repeated to keep the furnace filled and to move the material through it.

" When the furnace has been completely filled &

with loaded cars, the next operation will effeet the withdrawal from the furnace of a car of annealed material, which car is lowered to and pushed upon lower track 23 where it is unloaded. Thus the operation of the furnace and the movement of the material therethrough is made continuous.

llt will be observed from Figs. 2 and a that the tunnel, and particularly its heating zone, is of materially greater height than width. In each side of heating zone 5, and preferably also in each side of preheating zone 4, electric resistance elements are positioned for heating the sheets or other material being annealed, the arrangement being such that the cars of material pass between and relatively close to the heating elements so that there is little loss of heat. Preferably the heating elements are as shown in Fig. 9, attached to the side walls of the furnace, extending substantially from its top to its bottom. These elements, indicated as ribbons 110, 111 and 112, are preferably arranged in tiers, each independently controlled so that the heat generated by each tier ma be varied to meet difierent condi tions of operation with a view to obtaining the best annealing results. We have found that by this arrangement of heating elements in a narrow vertical tunnel through which metal is carried in an upright posi-v tion, the metal becomes thoroughly heated and annealed throughout in a short time.

Reference has been made to the maintaining of a non-oxidizing or reducing atmosphere in the furnace, and to the structural features of the furnace for preventing substantial loss of the gas or gases forming this atmosphere. While as far as concerns some features of our invention various gases or vapors may be used, we have discovered, and on this discovery our invention is in part predicated, that a certain mixture of nitrogen and hydrogen may advantageously be used, not merely to prevent oxidation of the metal being annealed, but to reduce the oxide coating which is customarily found on hot rolled or otherwise hot worked metal. Hydrogen has been used to reduce oxide coatings on hot Worked metal, but several disadvantages attend its use. It is liable to explode when mixed with air, and it has a deleterious effect upon certain metals, such as high carbon steel. To reduce the liability of explosions, it has been pro osed to use a mixture of an inert gas suci as nitrogen,

and hydrogen, but heretofore it has not been deemed possible to effect adequate reduction of oxide coated surfaces with a mixture sufficiently low in hydrogen content to be comparatively safe and comparatively inexpensive.

In the operation of the furnace shown herein we have discovered that by introducing into the furnace a mixture of nitrolltlll llltl llltli l rt lid

gen and hydrogen, with the hydrogen as low as three per cent of the mixture, the oxide coating on hot rolled nickel and nickel base alloy sheets is completely reduced during the annealing operation, the cooled annealed sheets being much brighter than when placed in the furnace. While this small percentage of hydrogen is suflicient, larger percentages, up to about fifteen per cent, may be used Without forming an explosive mixture even in the presence of air. The mixture of nitrogen and hydrogen is preferably introduced in the furnace at the portion of heating zone 5 adjacent to precooling zone 6, at which position the metal being annealed has reached its highest temperature. As shown in Figs. 9 and 10, the mixture of nitrogen and hydrogen may be introduced through a pipe extending through a side wall of the furnace and provided with discharge openings 116. By continuously supplying a stream of this gaseous mixture, there is provided a constant replenishment of the mixture to compensate for the small loss of gas during charging and discharging operations and by leakage, and there is also continuously supplied suficient hydrogen to reduce the oxide coatings on the metal being annealed. By analyzing the gas at theends of the furnace, we have found that it contains little, if any, free hydrogen, it being all, or substantially all, consumed in the furnace.

According to the provisions of the patent statutes, we have explained the principle and mode of operation of our invention, and have described and illustrated the preferred embodiment of it. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. A double deck continuous annealing furnace having a heating tunnel on the up per deck and a material handling section on the lower deck, a car track on each deck, an elevator at each end of the furnace for transferring cars from one to the other of said decks, an openin in the bottom of each end of the tunnel or receiving said elevators, means for sealing said openings when said elevators are in raised and lowered positions, said elevator having car tracks thereon, and means for displacing said elevator-car tracks to avoid interference between them and said sealing means when the elevators are moved.

2. A double deck continuous annealing furnace, having a heating tunnel on the upper deck and a car transferring section on the lower deck each provided with a track, an elevator at each end of the furnace for moving cars from one to the other of said decks, a longitudinally movable car track steaaseo borne by each elevator, an opening in the bottom of the tunnel at each end thereof for receiving the elevators, means for sealing said openings when the elevators are in their raised and lowered positions, and means coordinated with the movements of each elevator for moving its car track longitudinally to clear them from said sealing means and to bring them in operative continuity with the tracks in the; tunnel and on the lower deck. 7

3. A continuous annealing furnace comprising a tunnel having an elevator shaft leading thereinto and provided with a track, an elevator in said shaft having a floor provided with a longitudinally movable track, a track moving arm engaging said movable track, and means extending from said arm to said shaft for moving said arm as the elevator is raised and lowered, whereby said movable track is moved to and from registration with said tunnel track.

4. A continuous annealing furnace comprising a tunnel terminating in a charging chamber at one end and a discharging chant her at its other end, a car-supporting track in said tunnel, and a pivotally mounted member normally biased into car-engaging position to allow forward and prevent backward movement of the cars.

5. A continuous annealing furnace comprising a tunnel terminating in a charging chamber at one and a discharging chamber at its other end, a car-supporting track in said tunnel, means for moving cars on said track, means including a movable blocking member for engaging a car for preventing its forward movement into said discharging chamber, and an electro-magnet energized by the operation of said car-moving means for disengaging said blocking member.

6. A continuous annealing furnace comprising a tunnel of materially greater height than width, electric-resistance heating elements arranged in both sides of the tunnel and extending substantially from the top to the bottom thereof, and cars provided with means for holding in an upright position material to be annealed in the tunnel while the cars move through it between said heat ing elements.

7. A continuous sheet annealing furnace comprising a tunnel having in succession heating and cooling zones and being of materially greater height than width, electricresistance heating elements arranged in both sides of the tunnel and extending substan tially from the top to the bottom thereof, means for introducing into the portion of said heating zone adjacent to the cooling zone a reducing atmosphere, and means for moving through said tunnel and in upright positions between said heating elements sheets to be annealed in the furnace.

8. A continuous annealing furnace com- BOT:

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prising a tunnel including a heating zone having partitions provided with openings arranged therein, a train of cars arranged in said tunnel for movement therethrough, each of said cars being provided with a heat resisting end barrier approximating the shape of the openings in said partitions, the distances between said partitions being multipies of the lengths of said cars so that when the train is not in motion a car end barrier is disposed in the opening in each partition to prevent the escape of hot gases therethrough and whereby with each succeeding movement of the train one car length places other end barriers in the partition openings.

In testlmony whereof, we hereunto sign 0111' names.

HENRY ALINDER. GRANT B. SHIPL'EY. 

